1. Center of Gravity

2. Challenge: Leg Lift

3. Stable vs. Unstable

4. Stable Structures
The forces of gravity acts on all parts of the structure
All parts are evenly distributed around the center of gravity
= the structure is stable

6. Unstable Structures
A structure may collapse if the external forces causes the structure to become unbalanced
Also known as an “unbalanced” structure

8. Firm Foundation The foundation must be stable.
If not, compressive forces may cause structure to tip and become unstable.
Soil type and formations critically important in building planning

9. Build on FIRM FOUNDATION!!!
Leaning Tower of Pisa
Build on FIRM FOUNDATION!!!

10. Class Challenge: Super Glue Chair

11. Center of Gravity

13. What is center of gravity?
The center of gravity is the specific point where all of the mass of the structure is evenly distributed around

14. Mass vs. Weight Mass Amount of matter in an object Weight
Force of gravity felt on that object

16. What is “equilibrium”
A state in which opposing forces or influences are balanced in a “system”
A state of physical balance

17. What is a “system”
A structure made up of parts all related to one another

18. Challenge: The Impossible Leap

19. Ways to Increase Stability
Lower the center of gravity = widening structure
Increase speed (bike)

21. Ruler Experiment

22. Experiment: Spoon & Fork
Steps
Hand in your graphic organizer.
In partners of 2, get a spoon, fork, toothpick and a beaker
Put fork and spoon together
Add toothpick
Find center of gravity by balancing on table
*Bonus* - break off toothpick where center of gravity is
Draw your “system” and label. Include center of gravity, equilibrium line. Explain why the “system” is balanced (ie: why is it balancing?)